Rotary kiln

ABSTRACT

Disclosed is a rotary kiln that can be used efficiently in drying, dry distillation and incineration of various garbage and industrial wastes. 
     The rotary kiln comprises a cylindrical furnace body ( 10 ) disposed to incline at a small angle from the horizontal plane, a cylindrical contact heater ( 20 ) supported in the furnace body ( 10 ), a rotation drive means ( 30 ) that drives the furnace body ( 10 ) and the contact heater ( 20 ) to rotate, a waste charging port ( 61 ), a processed material discharging port ( 18 ), a combustion gas supply means ( 40 ) that supplies a combustion gas into the cylindrical contact heater ( 20 ) and a combustion gas introducing means ( 50 ) that guides the combustion gas through the contact heater ( 20 ) from a distal end to a proximate end thereof, and then guides the combustion gas through a space (S) between the contact heater ( 20 ) and the furnace body ( 10 ) from the proximate end to the distal end, thereby to charge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/JP00/06482 filed onSep. 21, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary kiln which can be preferablyused as a pretreatment furnace, and a drying furnace or dry distillationfurnace for drying or dry distillation of kitchen garbage that includesmuch water content. The rotary kiln can also be used as a recombustionfurnace that burns unburned components included in incineration ash.

2. Description of the Prior Art

Various rotary kilns comprising a rotatable cylindrical furnace bodyhave been provided. Most of these rotary kilns are operated by simplyrotating the cylindrical furnace body so as to move the waste throughthe inside of the furnace from one end to the other end, during whichthe waste is dried or burned and discharged. In a version of rotary kilnthat utilizes a high-temperature gas, a common practice is that thehigh-temperature gas is introduced from the end of the furnace body in acounter flow against the movement of the waste, so as to dry or burn thewaste by means of the high-temperature gas.

Also there is such a rotary kiln that utilizes high-temperature gas thathas a baffle plate disposed in the furnace thereby improving the effectof contact between the waste and the high-temperature gas.

An object of the present invention is to provide a rotary kiln capableof processing wastes with a higher heat efficiency.

SUMMARY OF THE INVENTION

The rotary kiln according a first aspect of the present invention, inorder to achieve the object described above, comprises a cylindricalfurnace body disposed to incline at a small angle from the horizontalplane, a cylindrical contact heater supported in the furnace body alongthe longitudinal direction thereof, a rotation drive means that drivesthe furnace body and the contact heater to rotate around the center axisof the cylinder, a waste charging port through which the waste ischarged into the furnace at a proximate end thereof, a discharging portprovided at the distal end for discharging the processed material thathas been moved from the charging port, a combustion gas supply meansthat supplies a combustion gas into the cylindrical contact heater atthe distal end thereof and a combustion gas introducing means thatguides the combustion gas, that has been supplied from the combustiongas supply means, through the contact heater from the distal end to theproximate end thereof, and then guides the combustion gas, that has beenreleased from the proximate end into the furnace body, through a spaceformed between the contact heater and the furnace body from theproximate end to the distal end of the furnace body, thereby todischarge the combustion gas through the distal end of the furnace bodyto the outside.

According to the first aspect of the present invention described above,the furnace body and the contact heater that is supported in the furnacebody are driven to rotate by the rotation drive means. The waste chargedinto the furnace body at the proximate end thereof moves through thefurnace body, that is inclined at a small angle from the horizontalplane, from the proximate end to the distal end while repeating a cycleof being raised and dropped off along the inner surface of the furnacebody as the furnace body rotates. Meanwhile the combustion gas, that hasbeen supplied from the combustion gas supply means into the cylindricalcontact heater at the distal end thereof, heats the contact heater to ahigh temperature while passing through the contact heater from thedistal end to the proximate end thereof. When coming out of the contactheater, the combustion gas U-turns and flows through the space betweenthe contact heater and the furnace body from the proximate end towardthe distal end while making contact with the waste, before beingdischarged from the discharging port.

The waste is heated not only by the inner surface of the furnace body,but also by the combustion gas and through contact with the outersurface of the contact heater, while moving through the furnace body.The waste is dried, experiences dry distillation (in case the atmosphereis made deplete of air), or burned, depending on the combustion gastemperature.

The rotation drive means can be constituted from a rotation drivemachine such as a motor, a speed reducer, a transmission chain, or thelike, so as to drive the furnace body and the contact heater eithertogether or separately.

The combustion gas supply means can be constituted from a burner, asupply tube for supplying the combustion gas generated by a burner intothe contact heater, or other suitable means.

The combustion gas guiding means can include a fan that generates anegative pressure for introducing the gas, and/or air flow regulatingmeans such as damper, or the like.

According to the first aspect with the constitution described above,since the contact heater is installed in the furnace body and thecombustion gas is brought into sufficient contact with the waste whileflowing through the contact heater and making a U turn, the waste isdried not only through contact with the combustion gas, but also throughcontact with the contact heater that has been heated sufficiently, thuscapable of very efficient drying, dry distillation and/or incineration.

In addition to the constitution of the first aspect described above, arotary kiln according to a second aspect of the present invention isprovided with rake up means installed on the inner surface of thefurnace body that rakes up the waste, that has been charged into thefurnace body, along the circumferential direction of the cylinder as thefurnace body rotates.

According to the second aspect described above, in addition to theoperation and effects of the first aspect, the waste that has beencharged into the furnace body is raked up to a position sufficientlyhigh by the rake up means installed on the inner surface of the furnacebody and then falls off by gravity, as the furnace body rotates. Whenfalling, the waste rests on the contact heater so as to make contactwith the outer surface of the contact heater and is heated further. Asthe contact heater rotates, the waste is caused to fall bit by bit atdifferent positions, so as to fall again separately onto the innersurface of the furnace body. The waste repeats this cycle until it isdischarged out of the furnace body.

Thus according to the second aspect of the present invention, the wastecan be brought into contact with the combustion gas with a higherefficiency by sufficiently stirring the waste in the furnace body, andthe waste can be brought into contact with the contact heater with ahigh efficiency, making it possible to carry out drying, drydistillation and incineration with high efficiency.

In addition to the constitutions of the first and second aspectsdescribed above, a rotary kiln according to the third aspect of thepresent invention is provided with slip preventing means installed onthe inner surface of the furnace body that prevents the waste chargedinto the furnace body from slipping and moving too fast toward thedistal end.

According to the third aspect described above, in addition to theoperations and effects of the first and second aspect, such an effect isachieved as the waste charged into the furnace body is prevented, by theslip preventing means installed on the inner surface of the furnacebody, from slipping and moving too fast toward the distal end. While toofast a movement of the waste may cause the waste to be dischargedwithout being sufficiently heated for drying, dry distillation orincineration, installing the slip preventing means enables it to movethe waste through the furnace body with a predetermined proper retentiontime.

In addition to any one of the constitutions of the first to thirdaspects described above, a rotary kiln according to a fourth aspect ofthe present invention is provided with one or a plurality of vanesdisposed around the circumference of the cylindrical contact heaterextending radially therefrom, so that the waste that falls off afterbeing raised along the inner surface of the furnace body as the furnacebody rotates, on the vane so as to promote contact heating and, at thesame time, the waste falls from the vane onto the inner surface of thefurnace body again in a scattered state.

According to the fourth aspect described above, in addition to theoperations and effects of any one of the first to third aspects, such aneffect is achieved as the area of contact with the waste is increased bymaking such a configuration of the contact heater installed in thefurnace body as the vane is installed around the circumference of thecylindrical contact heater extending radially therefrom, therebyincreasing the area of contact with the waste and conveniently receivingthe waste falling off from near the top in the furnace body, thus makingit possible to efficiently process the waste including drying, drydistillation and recombustion of the unburned material included in theincineration ash. Also because the waste falls while being dispersedonto different positions of the inner surface of the furnace bodydepending on the angular position of the vane as the contact heaterrotates, the waste can be prevented from being concentrated therebyensuring proper processing performance.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention willbecome apparent from the detailed description contained herein below,taken in conjunction with the drawings, in which:

FIG. 1 is a longitudinal sectional view of an example of a preferredrotary kiln according to the present invention.

FIG. 2 is a sectional view taken along lines X—X of FIG. 1;

FIGS. 3(A), 3(B), 3(C) and 3(D) show different angular positions of therotating contact heater and the direction of the waste falling off;

FIG. 4 is a sectional view showing another example of the contactheater; and

FIG. 5 is a sectional view showing a further example of the contactheater.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of preferred rotary kiln according to the present inventionwill be described below with reference to FIG. 1 to FIG. 3.

The rotary kiln shown in FIG. 1 to FIG. 3 is made in a horizontalconfiguration. The rotary kiln comprises a furnace body 10, a contactheater 20 that is supported in the furnace body 10 along thelongitudinal direction thereof, a rotation drive means 30 that drivesthe furnace body 10 and the contact heater 20 to rotate, a combustiongas supply means 40 that supplies a combustion gas into the contactheater 20, a combustion gas guiding means 50 that guides the combustiongas that has been supplied into the contact heater and the furnace body10, and an outer casing 60.

The furnace body 10 has a cylindrical shape and is supported by a pairof support roll assemblies 70 so as to be inclined at a small angle fromthe horizontal plane. The furnace body 10 is driven by the rotationdrive means 30 to rotate around the center axis of the cylinder.Accordingly, the waste that is charged into the furnace body 10 at theproximate end thereof through the charging port 61 moves toward thedistal end while repeating a cycle of being raised and falling off asthe furnace body 10 rotates.

The furnace body 10 is constituted from a heat resistant cylinderconsisting of an outer cylinder 11 and an inner cylinder 12, and isprovided with ring rails 13 that facilitate rotation on the supportrolls 70 and a sprocket 14 for transmitting the rotation drive force ofthe rotation drive means 30.

The inner cylinder 12 has, on the inner surface thereof, a plurality of(in the example shown, eight) rake-up ridges 15 disposed at constantintervals along the circumference, running in the longitudinal directionof the cylinder. The rake-up ridges 15 are provided for raising thewaste that is charged into the furnace body 10 efficiently along thecircumference as the furnace body 10 rotates, and rake up the wastealong the circumference as the furnace body 10 rotates.

The inner cylinder 12 has, on the inner surface thereof, a plurality of(in the example shown, three) ring-shaped slip preventing ridges 16disposed at constant intervals in the longitudinal direction of thecylinder running along the circumference. The ring-shaped slippreventing ridges 16 prevent the waste that is charged into the furnacebody 10 from slipping toward the distal end.

The contact heater 20 heats up the waste through contact therewith, andalso scatters the waste in the furnace body 10 so that the waste willnot be concentrated.

The contact heater 20 has a generally cylindrical configuration so as toallow the combustion gas to pass therethrough from the distal end to theproximate end thereof. As the combustion gas passes the inside, thecontact heater 20 is heated to a high temperature. The combustion gasthat has passed the contact heater 20 is discharged through outlet 21provided at the proximate end of the contact heater 20 into the furnacebody 10.

The contact heater 20 is fixed onto the furnace body 10 (at three pointsin this example) by means of support 17. The contact heater 20 issupported concentrically in the cylindrical furnace body 10, and rotatesaround the center axis together with the furnace body 10.

The contact heater 20 has vanes 22 disposed around the circumferencethereof extending radially therefrom. Installing the vanes 22 increasesthe chance of making contact with the waste, and also makes it possibleto heat the waste that falls off after being raised in the furnace body10 as it rotates, by receiving the waste on the vanes so as to promotecontact heating and let the waste fall in a scattered state.

In the example shown in FIG. 1 to FIG. 3, a pair of the vanes 22 aredisposed on the circumference, so that the contact heater 20 has aflattened cylinder shape overall. The number of the contact vanes 22provided on the contact heater 20 may not be necessarily be two. Thecontact heater may have the form of a contact heater 120 that has threevanes 122 disposed around the circumference thereof extending radiallytherefrom as shown in FIG. 4. Also the contact heater may have the formof a contact heater 220 that has four vanes 222, as shown in FIG. 5.There is no restriction on the number of the vanes.

The rotation drive means 30 has a motor 31 with a speed reducer, asprocket 32 and a transmission chain 33, so that as the motor 31 runs,the furnace body 10 is driven to rotate via the sprocket 32, thetransmission chain 33 and the sprocket 14 of the furnace body 10. As thefurnace body 10 rotates, the contact heater 20 also rotates therewith.

The combustion gas supply means 40 has a burner 41 such as gas burner orpetroleum burner, and a supply tube 42 that supplies the combustion gasgenerated in the burner 41 into the contact heater 20 has its tipextending into the contact heater 20 through the distal end thereof. Thejoint of the supply tube 42 and the contact heater 20 is sealed so asnot to allow the gas to leak.

The combustion gas guiding means 50 comprises an exhaust gas collectionchamber 51 that is a space immediately following the discharge port 18opening at the distal end of the furnace body 10, installed adjacent tothe outer casing 60, an exhaust gas discharge port 52 installed in theceiling of the exhaust gas collection chamber 51, and an exhaust fan 53that forcibly extracts the exhaust gas.

When the exhaust fan 53 runs, the combustion gas supplied from theburner 41 through the supply tube 42 into the contact heater 20 isguided to flow through the contact heater 20 from the distal end to theproximate end thereof, while heating the contact heater 20. Thecombustion gas then exits from the contact heater 20 through the gasoutlet 21 provided at the proximate end thereof so as to enter thefurnace body 10, and flows through the space S between the contactheater 20 and the furnace body 10 toward the distal end of the furnacebody 10. The combustion gas makes contact with the waste in thisprocess. The combustion gas flowing through the space S toward thedistal end exits the furnace body through the exhaust port 18 of thefurnace body 10 and enters the exhaust gas collection chamber 51, fromwhich it is discharged through the exhaust port 52 to the outside of theapparatus.

The outer casing 60 shields the furnace body 10 and other componentsthat reach a high temperature, and has a charging port 61 for the waste.Under the exhaust gas collection chamber 51 that may be a part of theouter casing 60, a takeout port 62 is provided for removing the wastethat has been discharged from discharging port 18 of the furnace body10, out of the apparatus. The waste charged through the charging port 61into the furnace body 10 moves from the proximate end to the distal endwhile repeating the cycle of being raised and falling as the furnacebody 10 rotates.

A description will be given below for the operation of processing thewaste in the rotary kiln of the present invention having theconstitution described above.

In case the rotary kiln of the present invention is used for dryingwaste such as kitchen garbage that includes much water content prior toincineration, temperature of the combustion gas delivered from theburner 41 is set to a temperature appropriate for drying the waste suchas kitchen garbage that includes much water. The speed of moving thewaste through the furnace body is also optimized. In case the rotarykiln of the present invention is used for dry distillation of citygarbage and industrial waste, temperature and oxygen concentration ofthe combustion gas are set to appropriate values. In case the rotarykiln of the present invention is used for recombustion of unburnedcomponents included in incineration ash, temperature of the combustiongas and the combustion air concentration are controlled accordingly.

Now the operation will be described with reference to FIG. 3, in casewaste is charged through the charging port 61 into the furnace body 10that is rotating, while combustion gas supplied from the burner 41 isintroduced into the contact heater 20. The waste that has been chargedmoves from the proximate end to the distal end while repeating the cycleof being raised by the rake-up ridges 15 to a high position on the innersurface of the furnace body 10 and falling off as the furnace body 10rotates. During this process, the contact heater 20 also rotates and theposition of the vanes 22 around the axis as shown in FIGS. 3(A) to FIG.3(D) depending on the angular phase of rotation. When the vane 22 is atthe position (A), the vane receives the falling waste and carries it toposition (B) while heating the waste through contact therewith. Atposition (B), the waste slips down along the inclined vane in thedirection indicated by an arrow. When the vane 22 receives the fallingwaste at position (C), the vane lets the waste fall right downward asindicated by an arrow while heating the waste through contact therewith.When the vane 22 is at the position (D), the falling waste is heatedwhile slipping down along the inclined vane in the direction indicatedby an arrow. Thus the contact heater 20 heats the waste through contacttherewith while rotating, and also scatters the waste so as to preventthe waste from being concentrated.

The waste is also heated through contact with the combustion gas andthrough contact with the inner surface of the furnace body 10 whilemoving through the furnace body 10.

INDUSTRIAL APPLICABILITY

As described above, the rotary kiln according to the present inventioncan be preferably used as a pretreatment furnace for incinerating citygarbage including kitchen garbage and a drying furnace or drydistillation furnace for drying or dry distillation of kitchen garbagethat includes much water. The rotary kiln can also be used as arecombustion furnace that burns unburned components included inincineration ash. The rotary kiln can be used as an efficient apparatusfor drying, dry distillation and incineration of various garbage andindustrial wastes by changing the combustion gas temperature and thequantity of oxygen supply according to the mode of processing the waste.

The foregoing relates to preferred exemplary embodiments in theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. A rotary kiln comprising a cylindrical furnace body 10 disposed toincline at a small angle from the horizontal plane, a cylindricalcontact heater 20 supported in said furnace body 10 along thelongitudinal direction thereof, a rotation drive means 30 that drivessaid furnace body 10 and said contact heater 20 to rotate around thecenter axis thereof, a waste charging port 61 for charging the wasteinto the furnace body at the proximate end thereof, a discharging port18 for discharging processed material that has moved from the chargingport 61 at the distal end of said furnace body 10, a combustion gassupply means 40 that supplies a combustion gas into said cylindricalcontact heater 20 at the distal end, a combustion gas guiding means 50that guides the combustion gas supplied from said combustion gas supplymeans 40 through said contact heater 20 from the distal end to theproximate end and then guides the combustion gas that has been releasedfrom the proximate end into the furnace body 10 through a space Sbetween said contact heater 20 and said furnace body 10 from theproximate end to the distal end, thereby to discharge the gas from thefurnace body 10 at the distal end thereof to the outside.
 2. The rotarykiln according to claim 1, wherein said furnace body 10 furthercomprising rake up means 15 on the inner surface thereof for raising thewaste that has been charged therein along the circumference as thefurnace body 10 rotates.
 3. The rotary kiln according to claim 2,wherein said contact heater 20 has at least one vane 22 disposed aroundthe center axis thereof extending radially therefrom, said at least onevane 22 receiving waste that falls off after being raised along theinner circumference of the furnace body 10 as the furnace body 10rotates so as to promote contact heating and let the waste fall off fromsaid at least one vane 22 onto the inner surface of the furnace body 10again in a scattered state.
 4. The rotary kiln according to claim 1,wherein said furnace body 10 comprises on the inner surface thereof,slip preventing ridges 16 for preventing waste that has been chargedinto said furnace body 10, from slipping and moving toward the distalend.
 5. The rotary kiln according to claim 4, wherein said contactheater 20 has at least one vane 22 disposed around the center axisthereof extending radially therefrom, said at least one vane 22receiving waste that falls off after being raised along the innercircumference of the furnace body 10 as the furnace body 10 rotates soas to promote contact heating and let the waste fall off from said atleast one vane 22 onto the inner surface of the furnace body 10 again ina scattered state.
 6. A rotary kiln comprising, a cylindrical furnacebody 10 disposed to incline at a small angle from the horizontal plane,a cylindrical contact heater 20 supported in said furnace body 10 alongthe longitudinal direction thereof, a rotation drive means 30 thatdrives said furnace body 10 and said contact heater 20 to rotate aroundthe center axis thereof, a waste charging port 61 for charging the wasteinto the furnace body at the proximate end thereof, a discharging port18 for discharging processed material that has moved from the chargingport 61 at the distal end of said furnace body 10, a combustion gassupply means 40 that supplies a combustion gas into said cylindricalcontact heater 20 at the distal end, a combustion gas guiding means 50that guides the combustion gas supplied from said combustion gas supplymeans 40 through said contact heater 20 from the distal end to theproximate end and then guides the combustion gas that has been releasedfrom the proximate end into the furnace body 10 through a space Sbetween said contact heater 20 and said furnace body 10 from theproximate end to the distal end, thereby to discharge the gas from thefurnace body 10 at the distal end thereof to the outside; wherein saidfurnace body 10 further comprising rake up means 15 on the inner surfacethereof for raising the waste that has been charged therein along thecircumference as the furnace body 10 rotates; and wherein said furnacebody 10 comprises on the inner surface thereof, slip preventing ridges16 for preventing waste that has been charged into said furnace body 10,from slipping and moving toward the distal end.
 7. The rotary kilnaccording to claim 6, wherein said contact heater 20 has at least onevane 22 disposed around the center axis thereof extending radiallytherefrom, said at least one vane 22 receiving waste that falls offafter being raised along the inner circumstance of the furnace body 10as the furnace body 10 rotates so as to promote contact heating and letthe waste fall off from said at least one vane 22 onto the inner surfaceof the furnace body 10 again in a scattered state.
 8. A rotary kilnaccording comprising, a cylindrical furnace body 10 disposed to inclineat a small angle from the horizontal plane, a cylindrical contact heater20 supported in said furnace body 10 along the longitudinal directionthereof, a rotation drive means 30 that drives said furnace body 10 andsaid contact heater 20 to rotate around the center axis thereof, a wastecharging port 61 for charging the waste into the furnace body at theproximate end thereof, a discharging port 18 for discharging processedmaterial that has moved from the charging port 61 at the distal end ofsaid furnace body 10, a combustion gas supply means 40 that supplies acombustion gas into said cylindrical contact heater 20 at the distalend, a combustion gas guiding means 50 that guides the combustion gassupplied from said combustion gas supply means 40 through said contactheater 20 from the distal end to the proximate end and then guides thecombustion gas that has been released from the proximate end into thefurnace body 10 through a space S between said contact heater 20 andsaid furnace body 10 from the proximate end to the distal end, therebyto discharge the gas from the furnace body 10 at the distal end thereofto the outside; and wherein said contact heater 20 has at least one vane22 disposed around the center axis thereof extending radially therefrom,said at least one vane 22 receiving waste that falls off after beingraised along the inner circumference of the furnace body 10 as thefurnace body 10 rotates so as to promote contact heating and let thewaste fall off from said at least on vane 22 onto the inner surface ofthe furnace body 10 again in a scattered state.